How many people actually put a time limit on somebody borrowing something? That doesn't actually mean that you have the right to use it in perpetuity. I've borrowed tools from my neighbor. He didn't tell me "You can use my weed whacker until 6 PM tonight" but it was understood that I should return it, and that I should ask him for permission if I wanted to use it again.
Reasonable people understand that if the owner wants their belongings back, the borrower is expected to return it.
Quite. I lent a book to a friend, I wasn't going to need it for a while and he was interested in it - I didn't give him a time-limit, I didn't see him at all over the summer...then I did need it back so I dropped him a message the day before I was going to see him, and he gave the book back.
Sorry it's not quite the same bouncy tale of entitlement and theft...but lending is not the same as giving, and civilised people know the difference.